The present invention relates to a small sized picture-taking lens using a solid picture-taking element such as a CCD type image sensor or a CMOS type image sensor, an image pick-up unit and a hand-held decive provided herewith.
Recently, following the technical advantage, size reduction of an image pick-up apparatus using a solid picture-taking element such as a CCD (Charge Coupled Device) type image sensor or a CMOS (Complementary Metal Oxide Semiconductor) type image sensor, a mobile phone provided with the image pick-up apparatus or a mobile information terminal is propagating. Further, for the picture-taking lens mounted in these image pick-up apparatus, the requirement for the further size reduction rises.
As an picture-taking lens for such a use, because the technical advantage can be obtained as compared with a lens of single lens or 2-lens composition, a lens of 3-lens composition is well known. A so-called triplet type picture-taking lens composed of, in an order from an object side, the first lens having a positive refractive power, the second lens having a negative refractive power, the third lens having a positive refractive power, is disclosed, for example, in Patent Document 1.
Further, a so-called tele-photo type picture-taking lens composed of, in order from an object side, the first lens having a positive refractive power, the second lens having a positive refractive power, the third lens having a negative refractive power, is disclosed, for example, in Patent Document 2.    [Patent Document 1] Tokkai No. 2001-75006    [Patent Document 2] Tokkai No. 2003-322792
However, the picture-taking lens which is a type disclosed in Patent Document 1 is a type in which, while a wide image angle is secured, aberrations are collected well, however, on the one hand, the total length of the picture-taking lens (a distance on the optical axis from the most object side surface of the picture-taking lens to the image side focal point) is comparatively long, and it can not be said that the lens is not always appropriate for the size reduction. Further, the picture-taking lens which is a type written in Patent Document 2, is a structure which is advantageous for reducing the total length of the picture-taking lens, however, there is a scope of betterment for the further size reduction.